1. Technical Field
The present invention relates to an electronic device including a circuit substrate, a circuit substrate for an electronic device, an electronic apparatus, and a moving object.
2. Related Art
As an electronic device of the related art, for example, a crystal oscillator having a so-called double-sided mountable structure in which a quartz crystal vibrator element (piezoelectric vibration element) is provided on a surface of a substrate section, and a quartz crystal terminal (mount pad) that is electrically connected to the quartz crystal vibrator element and an electronic component (integrated circuit element) that is electrically connected to the quartz crystal terminal are provided on a back surface thereof as described in JP-A-2010-178170 is known.
In the crystal oscillator, in response to the requirement for reduction in size, a smaller electronic component has been used, and also the mounting surface of the circuit substrate has been designed to have a small area.
The electronic component is mounted on, for example, the circuit substrate, and is connected to the quartz crystal terminal through metal bumps. Generally, the advancement of techniques for reducing the area of metal bump disposition has been slower than the advancement of integration techniques.
Therefore, in the crystal oscillator, the proportion of the area of the quartz crystal terminal in the area of the circuit substrate is likely to increase as the reduction in size thereof proceeds.
Additionally, in the case of the crystal oscillator having the double-sided mountable structure, when the electrical characteristics of the quartz crystal vibrator element are checked, a probe pin is brought into contact with the quartz crystal terminal, and therefore the area of the quartz crystal terminal is greater than the area of other mount pads.
Meanwhile, the same number of quartz crystal terminals as the number of excitation electrodes in the quartz crystal vibrator element are prepared, and are disposed at preferable positions in consideration of the ease of contact with the probe pin and a countermeasure for the floating capacitance between a print substrate and the quartz crystal terminal that are mounted on the crystal oscillator.
However, in the crystal oscillator described in JP-A-2010-178170, the floating capacitance between the quartz crystal terminal and the excitation electrodes is not taken into account.
As the floating capacitance, for example, an equivalent parallel capacitance C0 that is generated between both electrodes in the quartz crystal vibrator element through the quartz crystal terminal may be used, and there has been a case in which, as the value thereof increases, the electrical characteristics of the electronic device deteriorate.
Particularly, since the progress in the reduction in size of the crystal oscillator also makes the substrate section thinner, the distance between the quartz crystal terminal and the excitation electrode decreases, and the floating capacitance is likely to increase.